Adaptive systems for truss and tower systems
17 May 2005-Vol. 5765, pp 843-852
TL;DR: In this paper, the authors focus on providing in-built smartness to handle both force and deformation when unanticipated loads up to 100 percent increase over a short duration act on these systems.
Abstract: Truss and tower systems are widely used in variety of applications ranging from industrial structures to space stations. Such systems are normally designed for specified loads and by using respective codes. But in certain cases, they may be subjected to loads over the design values due to earthquakes of higher intensity, cyclones or even man-made disasters like terrorist attacks. Then a need arises to protect these systems, if they serve lifeline activities, through some inherent means; and this paper focuses attention on one such aspect. The objective is to provide a "smart control", which comes into effect only when the specified loads are exceeded by certain margins.[3] To demonstrate the introduction of smartness, a three-dimensional, three-panel tower system is chosen. Actuators, which activate corrective control to externally applied forces at the nodes of the truss, are provided on the members of the truss. The control forces within an active control system are typically generated through actuators based on feedback information from the measured response of the structure. The measured responses are monitored by sensors, which based on a pre-determined control algorithm, apply appropriate control signal for operation of the actuators. The generation of control forces requires external power leading to an active control system. Such a self correcting structure can be termed as smart or adaptive structure. This paper focuses on providing in-built smartness to handle both force and deformation when unanticipated loads up to 100 percent increase over a short duration act on these systems. Analysis is made for loads at the rate of 1.25,1.5,1.75 and 2 times the design load on the tower. For each of these loads, the example highlights how suitable control forces are generated and how the system under combined action of unanticipated and control forces balance in such a manner as to keep the structural integrity during short duration unanticipated loads.
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TL;DR: In this article, numerical simulations are conducted to investigate scissor-jack dampers for controlling vibrations in a seismically excited flexible truss tower, and the results indicate that the system is effective in reducing both the displacement and absolute acceleration response of the tower without exceeding damper stroke capacity in most cases.
Abstract: SUMMARY
In the proposed work, numerical simulations are conducted to investigate scissor-jack dampers for controlling vibrations in a seismically excited flexible truss tower. For the scissor-jack damper, new equations are developed to model the amplification factor that account for large deformations of the damper assembly. The equations are validated using computer-aided design and are used to investigate the influence of vertical deformations on scissor-jack damper amplification. Then, seismic analysis is carried out for scissor-jack dampers installed on a 3D flexible truss tower. To reduce the computational effort, a bi-model method is employed to represent the 3D truss tower as a dynamically equivalent 2D model. To describe the interaction between the structure and scissor-jack dampers, the displacement-dependent amplification factors of the scissor-jack devices and the corresponding damper forces are calculated at each time step. The response of the tower with scissor-jack damper systems is simulated for a range of damping and four major earthquakes and time histories of the displacement and absolute acceleration at each level of the tower are obtained. Results indicate that the system is effective in reducing both the displacement and absolute acceleration response of the tower without exceeding damper stroke capacity in most cases, but that damping level and earthquake intensity are important factors in the consideration of scissor-jack dampers for flexible structures subject to seismic loads. Copyright © 2011 John Wiley & Sons, Ltd.
14 citations
Cites methods from "Adaptive systems for truss and towe..."
...Finally, active control using actuators has been studied and proven effective in abating the response of towers subject to dynamic loading [5]....
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TL;DR: In this paper, the gain matrix for active devices placed directly between masses on a truss tower is transformed for devices placed at multiple levels between masses, and the transformed gains are then used with the single-mode approach to determine the damper coefficients.
Abstract: In the present article, the gain matrix for active devices placed directly between masses on a truss tower is transformed for devices placed at multiple levels between masses. The transformed gains are then used with the single-mode approach to determine the damper coefficients. Numerical validation of the proposed method is provided for a 3D truss tower with a single damper installed at each level, and alternate damper configurations are investigated. Damper configurations in which at least one damper is located at a level between concentrated masses result in a tower response that is comparable to that of the optimal configuration.
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...E-mail: walshk@ohio.edu 1063 [Rengaraja et al., 2005]....
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